This invention lies in the field of electronic circuits for controlling access to areas, information, circuits, and so on. More particularly, it is an access control system in which a number of decimal digits are preselected and set into a storage means at a control point, as a code. At a point at which access is desired (access point), a plurality of signals are sequentially transmitted, which correspond to a second group of decimal digits. At the control point, the signals are received and decoded. If the decimal digits to which they correspond are the same series of decimal digits inserted into the storage means, access is gained.
In the prior art, numerous systems have been devised for controlling access. Many of these involve the use of specific types of physical tokens, cards, or keys which actuate switches in various combinations, etc. Such systems are relatively inflexible because the keys or cards are not easily changeable in case it is desired to change a combination or a code for gaining access. Other systems use multiconductor transmission means, etc.